One of the most common sites for pain in children and adolescents is the musculoskeletal system, including joint pain, bone pain, and muscle pain. Discomfort may arise from disease processes (e.g., inflammation associated with arthritis), may be related to central pain processing difficulties (e.g., juvenile fibromyalgia syndrome), or may be related to trauma or injury, typically focusing on a specific area of the body (e.g., back pain or neck pain). A recent study sought to better identify the etiology of musculoskeletal pain, which is a major first step in better grasping its epidemiology.³ Demographic, clinical, and laboratory data were gathered on over 400 pediatric patients presenting with musculoskeletal pain, swelling, or limitation of movement. The etiology of these difficulties was identified in over 97% of cases, with by far the most common being noninflammatory and mechanical conditions (42.2%), followed by rheumatic diseases (31%), infection-related disorders (21.6%), and malignancy (2.4%). Age differences were noted, such that the prevalence of rheumatic disease was higher in those over 12 years, whereas younger age was associated with higher prevalence of infectious issues.

Determining the incidence of headache in the pediatric population is difficult due to changing diagnostic criteria and attempts to apply adult diagnostic criteria to children. In a review by Hershey et al.,²⁷ it was concluded that up to 75% of children have had significant headaches by the age of 15 years, with up to 28% of adolescents describing symptoms consistent with migraine headaches. Previous meta-analytic reviews suggested a gradual increase in headache incidence over childhood with 37% to 51% of children reporting a significant headache by 7 years and up to 82% by 15 years.²⁸ A more recent meta-analysis of 64 crosssectional studies (including a total of 227,249 subjects) yielded an estimated overall mean prevalence of headache was 54.4%, with an overall mean prevalence of migraine at 9.1%.²⁹

The distinction between migraine and tension-type headache is often complex, particularly in pediatric headache. For example, when applying International Classification of Headache Disorders-II criteria to a large sample of German children age 7 to 14 years, Kröner-Herwig and colleagues³⁰ found that 7.5% of the headaches could be classified as migraine, 18.5% as tension-type, and the majority were unclassifiable. Virtanen et al.³¹ found that among children who were classified as having migraines at age 6 years, half were unchanged at age 13 years, whereas for 32%, there was a shift toward tension-type headaches. Other authors found a similar lack of stability in headache type over time with headache types shifting or disappearing entirely. For example, a 10-year longitudinal study of principally preadolescent children diagnosed with migraine, only 46% continued to have migraine and the frequency of attacks had diminished.³²

Therefore, the precise relationship between various types of headaches in children remains unclear. In addition, various authors report close relationships between headache pain and other difficulties, including neck pain,³³ back pain,³⁴ abdominal pain,³⁵ sleep disturbances,³⁶ fatigue,³⁷ epilepsy,^38,39 epistaxis,⁴⁰ psychiatric difficulties, and risk of suicide.^41,42,43

Nonetheless, headaches in children appear to be quite common; however, precisely what differentiates migraine headache from tension-type headaches is difficult to discern at times. Headaches increase in frequency and severity with age with a clear shift around the time of puberty and are more common and problematic in females, and health-related quality of life (HRQOL) may be significantly impacted.⁴⁴

Chronic abdominal pain accounts for 2% to 4% of pediatric visits. Hyams et al.⁴⁵ found that 75% of middle school and high school students reported abdominal pain, whereas 21% reported it was severe enough to affect activities, and 8% visited a physician for it. Like other pain problems, various definitions and correlates of persistent abdominal pain (recurrent abdominal pain, chronic abdominal pain, functional abdominal pain, functional gastrointestinal disorder [FGID] nonorganic abdominal pain, and psychogenic abdominal pain) have led to varying perspectives in its prevalence.

A recent study of parental reports of 4- to 18-year-olds in a representative community sample of the United States indicated that 23.1% had at least one FGID, with functional constipation and abdominal migraine being the most common (Rome III criteria). The Rome III criteria for abdominal pain-related FGIDs in children and adolescents include functional dyspepsia, irritable bowel syndrome (IBS), abdominal migraine, childhood functional abdominal pain, and childhood functional abdominal pain syndrome.⁴⁶ A revision of these criteria, Rome IV, will include additional categories that include motility disturbance, visceral hypersensitivity, altered mucosal and immune functioning, altered gut microbiota, and altered central nervous system processing, all of which reflect recent advances in the field and will likely lead to more insight into incidence and etiologies.⁴⁷

It appears that the roots of nonspecific abdominal pain may be identified quite early in development based on chart reviews of a cohort of children followed from birth to 5 years. Chitkara et al.⁴⁸ found an incidence of abdominal pain of unknown origin of 4.5/1,000 person years leading to repeated visits to the pediatrician. Finally, as was the case with prior pain problems, there is growing evidence the difficulties with chronic abdominal pain early in life are associated with the risk of future abdominal pain, other pain problems (e.g., headache), and broader somatic concerns later in childhood and beyond.^49,50

The earlier review should make it clear that there is an array of chronic and recurrent pain problems that affect children and adolescents. It is unwise, therefore, to focus on “chronic” or “recurrent” pain as a unified entity but rather as diverse syndromes, perhaps with certain common factors. As is discussed in the following text, a broad biopsychosocial perspective is deemed optimal, which embraces genetic, developmental, and environmental influences.

In the remainder of this chapter, we discuss the impact of persistent pain on children and offer a general approach to evaluating and managing it. A more detailed review on a number of more common entities is offered as well. Additional information on many of these problems is available in other sections of this book, such as Chapters 25, 49, 57, and 61.

In the position statement published by the American Pain Society, chronic pain in children was defined as the result of a dynamic integration of biologic processes, psychological factors, and sociocultural factors considered within a developmental trajectory.⁹⁴ Therefore, evaluating a child with chronic pain can be time-consuming and complicated as a multitude of factors contribute to its development and maintenance. Children who present with persistent pain often receive extensive evaluations by both primary care providers and specialists in different disciplines due to the complexity of the pain presentation and the associated symptoms. If the pain appears to result from a previously or newly identified organic disease (e.g., ulcerative colitis, SCD, cancer), the treatment focus is on addressing the underlying illness while simultaneously treating the associated pain symptoms. In other situations, the source of the pain may be known and often time-limited but may not be amenable to direct treatment, and therefore, the focus is typically solely on addressing the pain (e.g., persistent postoperative, posttraumatic, or postviral pain). For both of these groups of children, there is no need for an extensive search for an explanation for their pain and the clinician can focus on its treatment.

The more challenging situations and the emphasis of the majority of this chapter occur when no obvious pathophysiologic source of the pain has been identified. The child is suffering, the parents are frustrated, extensive evaluation is often undertaken, and no treatable disease process emerges to explain the pain. In these situations, the clinician must attempt to identify those children who may have an as yet undiagnosed underlying progressive disease process and separate them from those who have chronic pain syndromes, which although uncomfortable, do not represent life-threatening illness. This is not an easy task, given the inherent vagueness and subjectivity of the symptoms, the inadequacies of children as historians, the strong desire of most children and their families for an
“organic treatable diagnosis,” and the vast differential diagnosis. In these situations when source of pain does not have a clear or treatable organic etiology despite adequate evaluation, the treatment focus changes and is ultimately on educating the family and patient on the pathophysiology of chronic pain including the process of central sensitization and on the value of a biopsychosocial rehabilitative approach.

Initially, however, a delicate balance must be struck between adequate evaluation and overinvestigation. The physician must be comfortable that he or she has enough information to rule out potentially serious or life-threatening causes of pain on the one hand while avoiding an endless search for the underlying etiology of the discomfort on the other. Continued laboratory investigation often convinces the child and family that there must be a biologic explanation for the problem and suggests to them that the “answer” may be found in the next laboratory test. Clinicians may report that they are ordering additional tests “for the sake of completeness” and both clinicians and families often find it difficult to draw a diagnostic line in the sand where all are content with extent of the investigation. Furthermore, pediatricians do not always agree on the diagnostic approach. Konijnenberg and colleagues⁹⁵ highlighted this problem in a series of papers in which 17 different pediatricians reviewed the medical records of 134 children with unexplained chronic pain. Consensus of the group was defined as an agreement among 80% of the pediatricians on the panel. Yet, there was disagreement on diagnostic approach in over a third of the patients and on the primary cause of the pain in over one-half.⁹⁵ Unfortunately, this diagnostic uncertainty often leads to further excessive and expensive laboratory and imaging studies. It is particularly unfortunate if, after completing an extensive battery of tests, which are negative, the doctor implies that the problem must be solely psychological and refers the child to a mental health professional.

Therefore, one of the most critical aspects of the evaluation of the child with unexplained chronic pain is the development of a trusting relationship with the child and family⁹⁶ and their acceptance that the medical investigation has been sufficient to allow the primary focus of the encounter to be on the management of the pain regardless of its etiology.

Etiologically, chronic pain is thought to stem from an interplay between biologic vulnerability, psychological variables, and environmental variables which allow for abnormalities of sensory processing, enhanced responsiveness, and excitability in the central nervous system known as central sensitization and amplification. Central sensitization is discussed in numerous other chapters throughout this book in detail, but it is the term used to describe the dysfunction or pathology of the nervous system that results in an amplified responsiveness of the central nervous system to painful and nonpainful stimuli. This increased responsiveness of the nervous system is thought to be a key element in the development and maintenance of chronic pain.^97,98,99,100

These factors must be considered in the evaluation and treatment of all children with chronic pain. As outlined in the American Pain Society consensus statement,⁹⁴ a comprehensive clinical assessment of a child with chronic pain should include a complete medical and pain history including onset, intensity, quality, location, duration, variability, predictability, exacerbating, and alleviating factors with ongoing management and reassessment emphasizing functional improvements. The physical exam should include a complete neurologic exam, with observation of the child’s general appearance, posture, and gait. Although laboratory and radiologic studies may be useful if a specific disease is suspected, the diagnosis of a chronic pain condition is predominately made by history and physical exam and best assessed by a pediatric interdisciplinary pain management team typically including pain medicine clinicians, mental health providers, and physical and occupational therapists.⁹⁴

Traditional elements of the pain history for adults are applicable to evaluating chronic pain in children. Although younger children are developmentally less capable of presenting a coherent narrative, they are capable of reporting on specific aspects of their pain. Using developmentally appropriate tools, children are able to define pain intensity as well as radiation, exacerbating and relieving factors of the pain, and quality of the pain. Chronic pain in children has a significant impact on daily function which can be seen in school attendance and work quality, social relationships, and mood.⁷⁸ The history of impact on daily function should be integral in ongoing reassessment of pain management as improvement in function may occur well before a decrease in pain intensity. Roth-Isigkeit and colleagues⁶¹ studied 750 German school children and found that 30% to 40% reported restrictions in daily living secondary to pain. Chalkiadis’s¹⁰¹ study of chronic pain in Australian youth revealed that 71% of children had difficulty sleeping and over 90% were unable to be involved in sports.

Because evidence supports that early exposure to painful stimuli and other adverse events potentially predisposes the child to changes in nociception, it is important to be aware of the child’s medical history. Fitzgerald and colleagues’^{102,103,104,105} study of rat pups has demonstrated long-lasting hypersensitivity to pain from early tissue injury. Grunau and coworkers,^{106,107,108,109} in a series of papers, compared toddlers who were born prematurely to babies of normal gestation and birth weight and found differences in pain sensitivity and somatization. Measurable differences between the groups were found even when the children had reached 8 to 10 years. Anand and Scalzo¹¹⁰ has even suggested that there are increased rates of attention-deficit/hyperactivity disorder (ADHD), substance abuse, and anxiety in children who have been exposed to repeated neonatal pain and stress.

Another essential element to query is the history of pain problems in the family. Although some authors, such as Borge and Nordhagen,¹¹¹ question whether chronic pain symptoms run in families, on the whole, the majority of studies have suggested that parent and family history of pain are predictors of child pain. This pattern has been identified in children with rheumatologic disease,¹¹² recurrent abdominal pain, migraine, and fibromyalgia.¹¹³ The mediators of this phenomenon are unclear. They may be physiologic (such as altered pain thresholds) or psychological (e.g., social modeling of catastrophizing behavior) or most likely a combination of both. Regardless of the mediators for this phenomenon, it is essential that family history of pain be examined. The child’s pain cannot be adequately addressed if the parent’s pain is not recognized.

Psychological and social factors should be explored in children with chronic pain and their families regardless of the pain’s etiology. Such an exploration does not imply causation, but there is clearly a transactional relationship between chronic pain and anxiety and depression.^114,115 As is evident throughout this chapter, anxiety, depression, and other mental health concerns frequently co-occur with chronic pain and need to be assessed. Questions regarding anxiety, depression, and excessive irritability should be posed to both the child and his or her family. The use of existing standardized questionnaires has been described earlier in this chapter and should be encouraged. In addition to mental health concerns in the child, Eccleston and colleagues¹¹⁶ report that parents who have chronically ill children are often anxious and depressed (60% and 40%), and these symptoms may be a response to parenting a sick child or may predate the child’s illness.¹¹³ Chronic pain is likely to bring severe disruption to the social and family structure,^62,117 which should be examined as part of gathering the history of the pain and its impact.

The child’s school experience should also be explored in an effort to identify further impact on daily function.¹¹⁸ Increased school absenteeism is commonly reported in most chronic pain syndromes,¹¹⁹ widespread musculoskeletal pain,¹⁰ and abdominal pain.¹²⁰ This may be a result of underlying stress from learning disabilities, attentional problems, or social difficulties such as bullying. Frequent absences may also become a source of extreme stress for the child when faced with the need to reintegrate making a frank discussion about the child’s grades, competencies, social skills, friendships, and existing school accommodations a necessary part of the history gathering. The Pediatric Pain Screening Tool (PPST) is a 9-item screening tool available to identify factors associated with adverse outcomes among youth who present with pain complaints, providing risk stratification and potential guidance for effective pain treatment recommendation in the clinic setting.⁹⁶

Finally, red flags or alarm signs specific to the common functional pain syndromes that help delineate a need for additional investigation is discussed in specific sections pertaining to each syndrome (headache, abdominal pain, and musculoskeletal pain).

A thorough biopsychosocial assessment of the child with chronic pain is critical for individualizing pain treatment strategies. The clinician aims to gather detailed information about the child’s current pain and pain history and assess areas of child daily functioning that are disrupted by pain while considering the child’s developmental stage. Many evidence-based self-report questionnaires have been developed and validated across the pediatric age range, which complement a semi-structured interview. Assessment is considered an iterative process, with follow-up assessment conducted throughout treatment to track progress toward treatment goals.

Measurement of aspects of recurrent and chronic pain requires tools that measure the frequency, intensity, duration, time course, and activity interference due to pain. Validated measures have been developed to capture most of these domains (e.g., Eccleston et al.,¹²¹ Stinson et al.¹²²). Developmental considerations will guide selection of the most valid and reliable tool. In children ages 4 through 12 years, Faces Pain Scales have demonstrated good validity and reliability.¹²³ In youth 8 years of age and older, Visual Analogue Scales, using anchors such as “no pain” and “worst pain ever,” are considered most valid and reliable. The verbal Numerical Rating Scale (NRS) is often used clinically, on which participants rate their pain on an 11-point scale representing increasing pain intensity (e.g., 0 to 10). Data indicate that the NRS is a valid and reliable measure for ages 8 years and older.¹²⁴

In addition to assessment of pain intensity, there are other characteristics of pain (e.g., duration, frequency, pain quality, spatial distribution) that are important to evaluate in children with chronic pain. Daily monitoring of pain and using a diary or log provides information about pain patterns as well as variations in children’s behaviors (e.g., activities participated in) and emotions (e.g., positive or negative affect).¹²⁵ A body map identifies the spatial distribution of pain, including the number of pain locations, and indicates how widespread the pain is. It is also helpful to obtain information from parents and children about the history and course of the pain problem, including past and present treatments for pain, perceived efficacy of treatments, and beliefs about the cause of pain and expectancies for pain relief. Electronic pain diaries (e.g., smartphones and Web sites) have become increasingly used in children and adolescents to document chronic pain symptoms. For example, Stinson and colleagues¹²⁵ developed a multidimensional electronic diary to collect data on pain intensity, duration, location, and impact in adolescents with arthritis.

A critical area to assess is function. Measures such as the Functional Disability Inventory⁶³ and the Child Activity Limitations Interview¹²⁶ provide information about interference of pain in normal daily activities. These measures are brief and can be administered easily to document children’s functional disability at baseline and treatment progress. Many children with chronic pain conditions experience significant school impairment including a high number of absences from school and difficulties making academic progress.^127,128 Role functioning can be assessed on broadband measures, such as HRQOL and pain impact measures. To supplement interview and survey assessment, objective measures of school attendance and performance (e.g., report cards, attendance records) are useful to obtain.

There are several multidomain measures that can be used for efficient assessment of multiple domains of functioning. The Patient-Reported Outcomes Measurement Information System (PROMIS) is a National Institutes of Health initiative. The PROMIS Pediatric Cooperative Group developed self-report item banks to assess general health domains, including depressive symptoms, anxiety, mobility, pain interference, fatigue, peer relationships, and pain intensity in children.¹²⁹ When used as a comprehensive battery, 25-, 37- and 49-item versions are available to assess multiple domains. These measures are appropriate for children ages 8 to 17 years¹³⁰ and can be supplemented by a parent proxy report. The Bath Adolescent Pain Questionnaire¹³¹ assesses seven domains of functioning affected by pain (social functioning, physical functioning, depression, general anxiety, pain-specific anxiety, family functioning, and development), and a parent report is also available.¹³² The Pediatric Quality of Life Inventory¹³³ is a well-validated HRQOL measure for children (age 5 to 18 years) to self-report functioning in four broad domains (physical, emotional, social, school) and has a parent proxy instrument for younger children.

Psychosocial assessment is an important component in the assessment of a child with chronic pain in order to evaluate psychological, social, and family functioning which may contribute to pain or pain-related disability. Psychosocial assessment may consist of clinical interviews, administration of standardized psychological measures, and observation of child and family members. A detailed clinical interview should cover developmental, behavioral, and psychiatric concerns in the patient’s and family’s history. Potential stressors and areas of maladaptive coping should be inquired about as well as a comprehensive school history and history of peer and social relationships. Ideally, a separate psychosocial assessment is conducted with child and parent alone in order to obtain their individual perspectives. Many outpatient pediatric pain clinics use intake questionnaire packets that cover demographics, developmental history, and other aspects of psychological functioning in order to consistently obtain this information in the evaluation of new patients. Review of intake packets may then provide details that serve as a springboard for more focused clinical interviews or additional psychological assessments during the intake visit.

Depending on the particular presenting concerns, standardized psychological measures may be administered to screen for mental health diagnoses, in particular, anxiety and depressive symptoms, to assess coping behaviors and family functioning. A variety of standardized instruments can be used in the clinical setting with the advantage of obtaining a quick assessment of children’s psychological functioning given the limited time available for in-depth psychological evaluation in the medical setting. Many valid and reliable measures are available to assess anxiety and depression in youth such as the Revised Child Anxiety and Depression Scale,^134,135 and PROMIS Emotional Distress anxiety and depressive symptoms.¹³⁶ Posttraumatic stress disorder (PTSD) symptoms can be measured using standardized tools like the 24-item Child PTSD Symptoms Scale.¹³⁷

When psychological measures are used to screen for psychological distress, it is important to consider the limitations of self-report and, in particular, that children may want to present themselves in a favorable light (social desirability response bias), which has been described in children and adolescents with chronic pain.¹³⁸

Beyond general internalizing symptoms, it is also useful to assess pain-specific dimensions of anxiety (e.g., catastrophizing, pain-related fear). There are developmentally adapted versions of the Pain Catastrophizing Scale available to assess child catastrophic thoughts about pain¹³⁹ as well as parent catastrophic thinking about their child’s pain.¹⁴⁰ Other measures are available to assess pain-related anxiety, such as the Child Pain Anxiety Symptoms Scale¹⁴¹ and the Fear of Pain Questionnaire,¹⁴² which also has a parent report.¹⁴³

Parental and family functioning has also been a major area of focus in pediatric chronic pain assessment.⁸⁹ There are measures available to assess parent behaviors (e.g., frequently attending to pain symptoms or allowing avoidance of regular activities) that may contribute to pain-related disability (e.g., Adult Responses to Children’s Pain Questionnaire).¹⁴⁴ In addition, overall family functioning can be assessed with several measures including the Family Assessment Device.¹⁴⁵ In some cases, it may be important to screen parents for their own psychological distress, given the risk for high levels of caregiver stress in this population (e.g., Brief Symptom Inventory). For a comprehensive review of measures available to assess parental impact of chronic pain, see Eccleston et al.¹²¹

There are also measures of child coping that have been validated on pediatric chronic pain samples including the Pain Response Inventory¹⁴⁶ and the Pain Coping Questionnaire.¹⁴⁷ Measures of specific areas of coping, including catastrophizing, are available such as the Pain Catastrophizing Scale, Child Version (PCS-C).¹³⁹

Well-established measures of sleep in pediatric chronic pain include the Children’s Sleep Habits Questionnaire (CSHQ),¹⁴⁸ the Adolescent Sleep-Wake Scale (ASWS),¹⁴⁹ and the Adolescent Sleep Habits Scale (ASHS).¹⁴⁹ The CSHQ is a parent-report measure used to assess multiple aspects of sleep in school-age children (ages 4 to 10 years), including bedtime behavioral issues and symptoms of sleep disordered breathing.¹⁴⁸ The ASWS and ASHS are complementary measures of sleep quality and sleep habits, respectively. Although reliable and relevant to pediatric pain, all three questionnaires are lengthy and potentially burdensome to complete. A short form (10-item) of the ASWS was recently developed that may be useful to integrate into quick-paced tertiary care settings.⁹⁰ For a comprehensive review of available sleep measurement tools in pediatric pain, see de la Vega and Miró.¹⁵⁰

Information gathered from the physical examination in conjunction with the history can help differentiate a primary/functional pain disorder from pain secondary to an underlying disease. General appearance (sickly or well appearing) may be helpful, although individuals who are in pain for a prolonged period of time may look pale and wan. Growth parameters should be examined as chronic illness may well impede growth. Because of the association between chronic pain and postural orthostatic tachycardia syndrome, heart rate should be obtained both supine and standing.

The child should be asked to localize his or her pain. The differential diagnosis and intervention strategies are very different for generalized discomfort versus highly localized pain. Specific discussion of the examination of the back, abdomen, and joints is beyond the scope of this review, but regardless of the origin of the pain, the clinician should obtain general impressions of the child’s mood, cooperativeness, irritability, and eye contact along with a comprehensive neurologic exam and more focused musculoskeletal exam, noting the child’s gait and posture.

Although hypermobility does not predict future musculoskeletal pain in the preteen and adolescent population, literature currently supports the association of chronic musculoskeletal pain with hypermobility.¹⁵¹ The Beighton score is a valid measurement of generalized joint hypermobility in children. A score of 6/9 indicates hypermobility.¹⁵² When positive, discussion regarding hypermobility can be helpful both in its suggestion of biologic vulnerability to pain as well as providing guidance in the development of additional goals for physical therapy such as joint protection, postural control, and improved proprioception as a part of the multidisciplinary plan.^152,153,154 Regardless of the origin, a Beighton score should be calculated on all children with chronic pain.¹⁵⁵